Why is spectrophotometer used in the leather & textile footwear industry? In the leather & textile footwear industry, using a spectrophotometer to capture both color and appearance on a physical sample has greatly improved quality, consistency, and speed to market. To make color approvals on-screen, the digital color file must also be color-accurate when it is imported into the design software

1. SPECTROSCOPY
Tanvir Siddike Moin
University of Dhaka

2. 2
• Spectroscopy is the study of radiated energy and matter to determine their interaction and it does not create results
on its own.
• In the textile industry, using a spectrophotometer to capture both color and appearance on a physical sample has
greatly improved quality, consistency, and speed to market.
• To make color approvals on-screen, the digital color file must be color-accurate when it is imported into the design
software.
• Spectroscopy helps bridge that knowledge gap.
• It is a method of understanding molecules by measuring the interaction of light and matter.
• By analyzing the amount of light absorbed or emitted by a sample, we can determine the sample's components,
characteristics and volume.
Why Is Spectroscopy Used In Leather & Textile Footwear Industry?

3. Determining the Structure of an Chemical Compound
• The analysis of the outcome of a reaction requires that we know the full structure of the
products as well as the reactants
• In the 19th and early 20th centuries, structures were determined by synthesis and
chemical degradation that related compounds to each other
• Physical methods now permit structures to be determined directly.
• We will examine:
• Mass spectrometry (MS)
• Infrared (IR) spectroscopy
• Nuclear magnetic resonance spectroscopy (NMR)
• Ultraviolet-visible spectroscopy (UV-Vis)
• Atomic Absorption spectroscopy
3

4. 4
Spectroscopy:
• The study of the interaction of energy with matter
• Energy applied to matter can be absorbed, emitted, cause a chemical change, or be transmitted
• Spectroscopy can be used to elucidate the structure of a molecule
Examples of Spectroscopy
Infrared (IR) Spectroscopy
• Infrared energy causes bonds to stretch and bend
• IR is useful for identifying functional groups in a molecule
Nuclear Magnetic Resonance (NMR)
• Energy applied in the presence of a strong magnetic field causes absorption by the nuclei of some elements
• NMR is used to identify connectivity of atoms in a molecule
Mass Spectrometry (MS)
• Molecules are converted to ions by one of several methods (including bombardment by a beam of
electrons)
• The ions formed may remain intact (as molecular ions, M+), or they may fragment
• The resulting mixture of ions is sorted by mass/charge (m/z) ratio, and detected
Introduction

5. 5
E =
hc

where c = velocity of light
The Electromagnetic Spectrum
• Electromagnetic radiation has the characteristics of both waves and particles
• The wave nature of electromagnetic radiation is described by wavelength () or frequency (n)
• The relationship between wavelength (or frequency) and energy (E) is well defined
• Wavelength and frequency are inversely proportional (n= c/)
• The higher the frequency, the greater the energy of the wave
• The shorter the wavelength, the greater the energy of the wave

6. 6
Period (p) – The time required for one cycle to pass a fixed point in space.
Frequency (n) – The number of cycles which pass a fixed point in space per second.
n = 1/p ( s-1 = Hz )
• n depends on the source, but is independent of the propagating (transmitting) material.
Amplitude (A) – The maximum length of the electric vector in the wave (Maximum height of a wave).
Wavelength (l) – The distance between two identical adjacent points in a wave (usually maxima or minima).
Time or Distance
-
+
Electric
Field
0
Amplitude (A)
Wavelength ()
Wave Parameters

7. • The electromagnetic spectrum covers a wide range of wavelengths.
• The divisions are based on the methods used to produce and observe the
various types of radiation.
• For example, the wavelength range for gamma rays and x-rays overlap. If
the source is man-made, the radiation is usually considered x-rays. If the
radiation is naturally occurring, the radiation is usually considered gamma
rays.
7
The Electromagnetic Spectrum

8. 8
Types Spectroscopic Methods Based On EM Radiation

9. All atoms and molecules are capable of absorbing energy in accordance with their own
structure variation and so the kind and amount of radiation absorbed by a molecule
depend upon:
 The structure of the molecule.
 The number of molecules interacting with the radiation.
• When electromagnetic radiation is absorbed by a molecule, it undergoes transition
from a state of lower to state of higher energy.
• If the molecule is monatomic (consisting of one atom), the energy absorbed can only
be used to raise the energy levels of electrons.
• If the molecule consists of more than one atom, the radiation absorbed may bring
about changes in electronic, rotational, vibrational or translational energy.
Basic principle of Ultraviolet-Visible spectroscopy

10. Basic principle of UV spectroscopy
Molecular orbitals and electronic transition
• While two atoms form chemical bond, their atomic orbital combine together to form molecular orbital.
• Bonding orbital and antibonding orbital
• Bonding orbital energy level is always lower than that of the original atomic orbital
• Antibonding orbital energy - higher s , p orbitals and n electrons
• At room temperature, most of the atoms, molecules and electrons are in the lowest energy orbital
called ground state.
• The electron of atom (molecule) at ground state can absorb proton and transit to higher energy orbital
called excited state.
• Atom or molecule can absorb the radiation only when the energy of proton is equal to the energy
difference of the two orbitals
• Ultraviolet-visible spectroscopy corresponds to excitations of outer shell electron between the energy
levels that correspond to the molecular orbital of the systems.
• The band spectrum of molecule due to vibrational and rotational levels

11. Laws Of Spectrometry
• There are two laws which govern the absorption of light by the molecules.
• These are Beer’s law and Lambert’s law.
• Lambert’s law:
When a beam of monochromatic radiation is passed through a solution of an absorbing
substance, the rate of decrease in intensity of radiation with thickness of absorbing
medium is directly proportional to the intensity of the incident radiation.
-dI/db α I
-dI/db α I
-dI/db = K1I
-dI/I = K1db

12. Integrating the equation between the limits b=0 to b and I=I0 to I,
= 
I
I
I
dI
0
/

b
db
k
0
1
I = intensity of incident radiation.
dI = Infinitesimally small decrease in the intensity of radiation on passing through infinitesimally small
thickness db, of the medium.
-dI/db = rate of decrease in intensity with the thickness b
K1 = Proportionality constant or Absorption coefficient
-ln I/I0 = K1b
ln I0/I = K1b
2.303 log I0/I = K1b
log I0/I = K1b/2.303…………………………………… (1)

13. Beer’s law
• When a beam of monochromatic radiation is passed through a solution of an
absorbing substance, the rate of decrease in the intensity of radiation with the
concentration of the solute in the solution is directly proportional to the
intensity of the incident radiation.
-dI/dc α I
-dI/dc α I
-dI/dc = K2I
-dI/I = K2dc
c = concentration of absorbing medium
-dI/dc = rate of decrease in intensity with the concentration c
K2 = absorption co-efficient]

14. • Integrating the equation between the limits c=0 to c and I=I0 to I,
=
• -ln I/I0 = K2c
• ln I0/I = K2c
• 2.303 log I0/I = K2c
• log I0/I = K2c/2.303…………………………….(2)
Combining equation 1 and 2, we get
log I0/I = (K1K2/2.303) × bc
Or, A = abc

I
I
I
dI
0
/

c
dc
k
0
2

15. • Where,
• A = absorbance (no units, since A = log I0 / I)
• a = absorptivity. For a specific wavelength, absorptivity value is constant for a
particular solute.
The value of the constant depends on:
• the substance,
• the solvent,
• the wavelength,
• the units used for concentration
• and path length.
Beer’s – Lambert’s Law applies to a solution containing
more than one kind of absorbing substances, provided
there is no interaction among the various species.

16. Instrumentation
• UV visible spectrophotometer consists of the following parts-
• Radiation source
• Monochromator
• Sample compartment
• Detector
• Recorder

17. • The electrical excitation of deuterium or hydrogen at low pressure produces
a continuous UV spectrum. Both Deuterium and Hydrogen lamps emit
radiation in the range 160 - 375 nm. Quartz windows must be used in these
lamps and quartz cuvettes must be used, because glass absorbs radiation of
wavelengths less than 350 nm.
Various UV radiation sources are as follows
• Deuterium lamp
• Hydrogen lamp
• Tungsten lamp
Various Visible radiation sources are as follows
• Tungsten lamp
• Mercury vapor lamp
Radiation source:

18. Monochromator: All monochromators contain the following
component parts;
• An entrance slit
• A collimating lens
• A dispersing device (a prism or a grating)
• A focusing lens
• An exit slit

19. Sample compartment:
• The cell holding the sample should be transparent to the
wavelength region to be recorded.
• Quartz or fused silica cuvettes are required for spectroscopy in
the UV region.
• Silicate glasses can be used for the manufacture of cuvettes for
use between 350 and 2000 nm.
• The thickness of the cell is generally 1 cm. cells may be
rectangular in shape or cylindrical with flat ends.

20. • The photomultiplier tube is a commonly used detector in UV-Vis
spectroscopy.
• It consists of a photoemissive cathode (a cathode which emits electrons
when struck by photons of radiation), several dynodes (which emit several
electrons for each electron striking them) and an anode.
Detector

21. • The signal for the intensity of absorbance versus corresponding
wavelength is automatically recorded on the graph.
• The more the absorbance the less the transmittance.
• The signal from the detector is normally proportional to the intensity of
light incident on the detector and after amplification may be displayed as
transmittance or absorbance.
Recorder

22. UV-vis Spectrophotometer
Single-Beam UV-Vis Spectrophotometer
• Single-Beam spectrophotometers are often sufficient for making quantitative absorption
measurements in the UV-Vis spectral region.
• Single-beam spectrophotometers can utilize a fixed wavelength light source or a continuous source.

23. Single-Beam UV-Vis Spectrophotometer
• The simplest instruments use a single-wavelength light source, such as a light-emitting
diode (LED), a sample container, and a photodiode detector.
• Instruments with a continuous source have a dispersing element and aperture or slit to
select a single wavelength before the light passes through the sample cell.

24. Dual-Beam uv-vis Spectrophotometer
• In single-beam Uv-vis absorption spectroscopy, obtaining a spectrum
requires manually measuring the transmittance of the sample and solvent
at each wavelength.
• The double-beam design greatly simplifies this process by measuring the
transmittance of the sample and solvent simultaneously.

25. Instrumentation
• The dual-beam design greatly simplifies this process by simultaneously
measuring P( Irradiance= the energy per unit area in the light beam-W/m2)
and Po of the sample and reference cells, respectively.
• Most spectrometers use a mirrored rotating chopper wheel to alternately
direct the light beam through the sample and reference cells.
• The detection electronics or software program can then manipulate the P and
Po values as the wavelength scans to produce the spectrum of absorbance or
transmittance as a function of wavelength.

26. Array-Detector Spectrophotometer
• Array-detector spectrophotometers allow rapid recording of absorption
spectra.
• Dispersing the source light after it passes through a sample allows the use of
an array detector to simultaneously record the transmitted light power at
multiple wavelengths.
• There are a large number of applications where absorbance spectra must be
recorded very quickly. Some examples include HPLC detection, process
monitoring, and measurement of reaction kinetics.

27. • Fiber identification is important in the textile industry, fashion and design houses, and forensic science.
• UV-visible spectroscopy of textile fibers is one of the most common applications of the technique.
• Dyes and Pigments
• Textile Fiber Properties
• Textile Properties
• Specificity of the colour reaction
• Proportionality between colour and concentration
• Stability of the colour
Importance Of UV-visible Spectroscopy In Leather & Textile Footwear

28. Theory of Fourier Transfer Infrared Spectrometry
• For a molecule to absorb IR, the vibrations or rotations within a molecule must cause a net change in
the dipole moment of the molecule.
• The alternating electrical field of the radiation (remember that electromagnetic radiation consists of
an oscillating electrical field and an oscillating magnetic field, perpendicular to each other)interacts
with fluctuations in the dipole moment of the molecule.
• If the frequency of the radiation matches the vibrational frequency of the molecule, then radiation
will be absorbed, causing a change in the amplitude of molecular vibration.
• Provides information about the vibrations of functional groups in a molecule
• Therefore, the functional groups present in a molecule can be deduced from an IR spectrum
Because the speed of light, c, is constant, the frequency ν, n, (number of cycles of the wave per second) can complete
at the same time, must be inversely proportional to how long the oscillation is, or wavelength:
ν =
𝐶
λ
E = hν =
ℎ𝐶
λ

29. Because the atomic particles in matter exhibit wave and particle properties (though opposite in how much) EM
radiation can interact with matter in two ways:
• Collision – particle-to-particle – energy is lost as heat and movement
• Coupling – the wave property of the radiation matches the wave property of the particle and “couple” to the next
higher quantum mechanical energy level.
The atoms in a molecule are in constant motion.
The covalent bond between two atoms acts like a spring, allowing the atoms to vibrate (stretch and bend) relative to
each other.

30. Different Types of Vibrations
Stretching – Vibration or oscillation along the line of the bond
Bending – Vibration or oscillation not along the line of the bond

31. The main parts of IR spectrometer are as follows:
 IR radiation sources
 Monochromators
 Sampling cells
 Detectors

32. IR RADIATION SOURCE
Sources must emit radiations
Which must be
• Intense enough for detection
• Steady
• Extend over desired wavelength.
INCANDESCENT LAMP :
• It contains tungsten filament
• Longer life
NERNST GLOWER:
• Hollow rod
• Diameter: 2mm
• It provides maximum radiation atabout 7100 cm-1.
•More intense than globar source
IR radiation sources

33. GLOBAR SOURCE:
• Rod of sintered silicon carbide
• length :50mm ,diameter : 4mm
• It is heated to 1300 -17000 C
• Maximum radiation at 5200cm-1
ADV:
• Self-starting
• High intense beyond 15µ m
MERCURY ARC:
• A special high pressure mercury lamps are used.
• Maximum radiation at <200cm-1
IR radiation sources

34. They select desired frequencies from source.
There are two types:
Prism Monochromator:
It is again of 2 types:
a. Single pass Monochromator
b. Double pass Monochromator
II. Grating Monochromator
PRISM MONOCHROMATOR
Prism Monochromator types
Single pass Monochromator Double pass Monochromator
Grating Monochromator
MONOCHROMATORS

35. The material containing sample must be transparent to IR radiation
• Cells should be very narrower-----0.01 to 1mm
DETECTORS :
• Bolometer
• Thermocouple
• Thermisters
• Golay cell
• Photo conductivity cell
• Semiconductor detectors &
• Pyroelectric detectors
Bolometer
Golay cell
Thermocouple
Thermisters
Pyroelectric detectors
SAMPLE CELLS

36. • A source generates light across the spectrum of interest.
• A monochromater (salt prism or a grating with finely spaced etched lines) separates the source radiation into its
different wavelengths.
• A slit selects the collection of wavelengths that shine through the sample at any given time.
• In double beam operation, a beam splitter separates the incident beam in two; half goes to the sample, and half to
a reference.
• The sample absorbs light according to its chemical properties.
• A detector collects the radiation that passes through the sample, and in double-beam operation, compares its
energy to that going through the reference.
• The detector puts out an electrical signal, which is normally sent directly to an analog recorder.
• A link between the monochromater and the recorder allows you to record energy as a function of frequency or
wavelength, depending on how the recorder is calibrated.

37. • To determine the chemical formula for the textile fiber
• We can identify textile fiber qualitatively to see the FTIR spectra.
Importance of FTIR Spectroscopy in Leather & Textile Footwear

38. 38
• When a charged particle such as a proton spins on its axis, it creates a magnetic field.
Thus, the nucleus can be considered to be a tiny bar magnet.
• Normally, these tiny bar magnets are randomly oriented in space. However, in the
presence of a magnetic field B0, they are oriented with or against this applied field.
More nuclei are oriented with the applied field because this arrangement is lower in
energy.
Nuclear Magnetic Resonance Spectroscopy

39. 39
• In a magnetic field, there are now two energy states for a proton: a lower energy state with the nucleus
aligned in the same direction as B0, and a higher energy state in which the nucleus aligned against B0.
• When an external energy source (hv) that matches the energy difference (ΔE) between these two states
is applied, energy is absorbed, causing the nucleus to “spin flip” from lower energy state to the higher.
When the nuclei fall back to their lower energy state, the detector measures the energy released, and a
spectrum is recorded.

40. 40
• Nuclei in different environments absorb at slightly different frequencies, so they are
distinguishable by NMR.
• The frequency at which a particular nucleus absorbs is determined by its electronic
environment.
The electron density surrounding a given nucleus depends on the electronegativity of the attached
atoms.
1.When there is a high electron density around the nucleus. We say that the nucleus is shielded.
2. The more electronegative the attached atoms, the less the electron density around the nucleus.
We say that the nucleus is deshielded.

41. Instrumentation
 Sample holder
 Permanent magnet
 Magnetic coils
 Sweep generator
 Radiofrequency generator
 Radiofrequency receiver

42. Diagrametic representation of the process

43. Sample holder:
• Glass tubes are employed which are sturdy,practical and cheap
• 8.5cm long ,0.3 cm in diameter

44. Permanent magnet:
• These magnets are generally used in spectrometers operating upto 100mhz
• Magnetic field must be constant over long periods of time

45. Magnetic coils:
•It is not easy to vary the magnetic field of a large ,stable magnet.
•The problem can be overcomed by placing a pair of Helmholtz coils in the pole faces of pole
magnet.

46. Sweep generator:
• Generally the field sweep method is regarded as better because it is easy to vary H0 than the
RF radiation so as to bring about resonance in nuclei.

47. Radiofrequency generator:
• RF oscillator is used to generate radiofrequency.
• To achieve maximum interaction of the RF radiation with the sample the coil of oscillator is
wound around the sample container.
RF receiver:
The line shapes associated with absorption and
dispersion can be determined

48. NMR spectrophotometer

49. • NMR techniques are widely used in structure determination of newly synthesized materials
in textiles.
Importance of NMR Spectroscopy

50. Principles of Electron-Impact Mass Spectrometry
• Atom or molecule is hit by high-energy electron
• electron is deflected but transfers much of its energy to the molecule
• This energy-rich species ejects an electron
• forming a positively charged, odd-electron species called the molecular ion
• Atom or molecule is hit by high-energy electron from an electron beam at 10ev
• Molecular ion passes between poles of a magnet and is deflected by magnetic field
• If the only ion that is present is the molecular ion, mass spectrometry provides a way to measure the molecular
weight of a compound and is often used for this purpose.
• However, the molecular ion often fragments to a mixture of species of lower m/z.
• The molecular ion dissociates to a cation and a radical
• Usually several fragmentation pathways are available and a mixture of ions is produced.
• mixture of ions of different mass gives separate peak for each m/z
• intensity of peak proportional to percentage ofeach ion of different mass in mixture
• separation of peaks depends on relative mass
• mixture of ions of different mass gives separate peak for each m/z
• intensity of peak proportional to percentage of each atom of different mass in mixture
• separation of peaks depends on relative mass

51. Atom or molecule is hit by high-energy electron
e–

52. Atom or molecule is hit by high-energy electron
electron is deflected but transfers much of its
energy to the molecule
e–

53. This energy-rich species ejects an electron.

54. This energy-rich species ejects an electron.
forming a positively charged, odd-electron species
called the molecular ion
e–
+
•

55. Atom or molecule is hit by high-energy electron from
an electron beam at 10ev
e–
beam
forming a positively charged, odd-electron
species called the molecular ion
e–
+
•

56. Molecular ion passes between poles of a
magnet and is deflected by magnetic field
amount of
deflection depends
on mass-to-charge
ratio
highest m/z
deflected least
lowest m/z
deflected most
+
•

57.  If the only ion that is present is the molecular ion,
mass spectrometry provides a way to measure the
molecular weight of a compound and is often used for
this purpose.
 However, the molecular ion often fragments to a
mixture of species of lower m/z.

58. The molecular ion dissociates to a cation and a radical.
+
•

59. The molecular ion dissociates to a cation
and a radical.
+ •
Usually several fragmentation pathways are
available and a mixture of ions is produced.

60. mixture of ions of
different mass
gives separate peak
for each m/z
intensity of peak
proportional to
percentage of each
ion of different
mass in mixture
separation of peaks
depends on relative
mass
+
+
+
+
+
+

61. mixture of ions of
different mass
gives separate peak
for each m/z
intensity of peak
proportional to
percentage of each
atom of different
mass in mixture
separation of peaks
depends on relative
mass
+ + + +
+ +

62. Mass spectrophotometer consists of
• The inlet system
• The ion source {ionisation chamber}
• The electrostatic accelerating system
• The magnetic field
• The ion separator
• The ion collector{detector and readout system}
• The vacuum system

63. How does a mass spectrometer work?
Create ions Separate ions Detect ions

64. Flow chart representation of the process

66. Identifying dye from dyed textile fiber
Importance of Mass Spectroscopy

67. Atomic Absorption Spectroscopy
Flame AAS has been the most widely used of all atomic methods due to its simplicity, effectiveness and
low cost
• First introduced in 1955, commercially available since 1959
• Qualitative and quantitative analysis of >70 elements
• Quantitative: Can detect ppm, ppb or even less
• Rapid, convenient, selective, inexpensive
Fundamentals
Absorption and emission of light by compounds is generally associated with transitions of electrons between
different energy levels

69. • When solution of metalic salt is sprayed on to a flame, fine droplets are formed , due to the thermal
energy of the flame , the solvent in the flame is evaporated , leaving a fine residue, which are converted
to neutral atoms.
• These neutral atoms absorb radiation of specific wavelength , emitted by hollow cathode
lamp(HCL).hollow cathode lamp is filled with the vapour of element , which gives specific wavelength of
radiation.
• For the determination of every element, hollow cathode lamp is selected, which contains vapour of the
element to be analysed although this appear to be demerits of AAS , specificities can be achieved only by
the use of HCL.
• The intensity of light absorbed by the neutral atom is directly proportion to the concentration of the
element and obeys Beer's law over a wide concentration range.
• The intensity of radiation absorbed by neutral atoms is measured using photometric detectors (PMT)
• In AAS the temperature of the flame is not critical , since the thermal energy of flame isused to atomise
the sample solution to fine droplets , to form a fine residue and later to neutral atoms.
• The exitation of neutral atoms is brought about only by radiation from hollow cathode lamp and not by
the thermal energy of the flame.

70. • Sample is carried into flame or plasma as aerosol, vapour or fine powder
• Liquid samples introduced using nebuliser
Sample Introduction: liquid samples

71. AAS Instrument

72. The Simple Diagram For The AAS

73. Determination of heavy metals in textile materials by atomic absorption
spectrometry.
Important of Atomic Absorption Spectroscopy